Process for producing polycarbonate resin

ABSTRACT

The purpose of this invention is to produce a stabilized terminal-blocked polycarbonate resin with a limited number of the terminal hydroxy groups having excellent thermal stability, color stability and hydrolysis resistance by an industrially advantageous method using a terminal blocking agent. In the production of a polycarbonate by the melt-polycondensation of an aromatic dihydroxy compound with an aromatic carbonic acid diester in the presence of a polycondensation catalyst, a terminal blocking agent expressed by the following formula (1)                    
     [in the formula, R 1  is chlorine atom, methoxycarbonyl group or ethoxycarbonyl group; R 2  is an alkyl group having a carbon number of 1 to 30, an alkoxy group having a carbon number of 1 to 30, an aryl group having a carbon number of 6 to 30 or an aryloxy group having a carbon number of 6-30] is added after the melt-polycondensation to the system in an amount of 0.3 to 4 mol-equivalent based on the hydroxy terminal group amount of the polycarbonate at 200 to 350° C. under a pressure of 1,013 hPa (760 mmHg) or below for 0.1 second or longer and, thereafter, a stabilizer is added and kneaded into the system at 200 to 350° C. under a pressure of 1.333×10 5  hPa (10 5  mmHg) or below for 0.1 second or longer.

DETAILED DESCRIPTION OF THE INVENTION

1. Technical Field

This invention relates to a process for producing a polycarbonate resin.More particularly, this invention relates to a process for producing astabilized terminal-blocked polycarbonate resin having low hydroxyterminal group content and excellent thermal stability, color stabilityand hydrolysis resistance by an industrially desirable method using aterminal blocking agent.

2. Background Arts

Polycarbonate resin is being used in various uses owing to its excellentmechanical properties such as impact resistance and transparency. Knownprocesses for the production of polycarbonate resin include aninterfacial process comprising the direct reaction of a dihydroxycompound with phosgene and a melt process comprising thetransesterification of a dihydroxy compound with a carbonic acid diesterby heating under reduced pressure.

Production of polycarbonate resin usually passes kneading a stabilizerinto a polymerized polycarbonate, however, the process has a problem todeteriorate polymer qualities such as thermal stability, color stabilityand hydrolysis resistance when hydroxy terminal groups remain in thefinal product of the polycarbonate.

The specification of the Japanese Patent Laid-Open TOKKAIHEI 6-157739discloses a process for solving the above problem by using at least tworeactors in series and adding a terminal blocking agent to at least onereactor containing a polymer having an intrinsic viscosity of 0.20 dl/gor above at the inlet side of the reactor in the case of producing anaromatic polycarbonate resin by the melt-polycondensation of an aromaticdihydroxy compound with a carbonic acid diester. However, the control ofthe intrinsic viscosity of the final polycarbonate resin is difficult bythis process owing to the decomposition of the polycarbonate caused bythe reaction by-products, and a satisfiable solution is not yet found atpresent.

MEANS FOR SOLVING THE PROBLEMS

The object of the present invention relates to a process for producing apolycarbonate resin and is to provide an industrial process forproducing a stabilized terminal-blocked polycarbonate resin having alimited number of terminal hydroxy groups and excellent thermalstability, color stability and hydrolysis resistance by blocking theterminal groups taking advantage of the reactivity of the hydroxyterminal groups of a polycarbonate and adding a stabilizer to theterminal blocked polymer.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention comprises a process for producing a polycarbonateresin characterized by adding a terminal blocking agent under reducedpressure to a polycarbonate produced by melt polycondensation of anaromatic dihydroxy compound with an aromatic carbonic acid diester inthe presence of a polycondensation catalyst, kneading of the mixturethereof and then adding a stabilizer to the kneaded mixture.

A stabilized terminal-blocked polycarbonate resin having a limitednumber of hydroxy terminal groups on the polycarbonate with excellentthermal stability, color stability and hydrolysis resistance can beproduced by the polycarbonate resin production process of the presentinvention.

In the present invention, the polycarbonate subjected to the terminalblocking reaction is a polymer produced by the transesterification of anaromatic dihydroxy compound with an aromatic carbonic acid diester inthe presence of a polymerization catalyst in a molten state.

There is no particular restriction to the aromatic dihydroxy compound tobe used in the melt polymerization, and examples of the compound arebis(hydroxyaryl)alkanes such as 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane,bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-3-methylphenyl)propane and1,1-bis(4-hydroxy-t-butylphenyl)propane, bis(hydroxyaryl)cycloalkanessuch as 1,1-bis(4-hydroxyphenyl)cyclopentane and1,1-bis(hydroxyphenyl)cyclohexane, dihydroxyaryl ethers such as4,4′-dihydroxydiphenyl ether, dihydroxyaryl sulfides such as4,4′-dihydroxydiphenyl sulfide, dihydroxyaryl sulfoxides such as4,4′-dihydroxydiphenyl sulfoxide, and dihydroxyaryl sulfones such as4,4′-dihydroxydiphenyl sulfone. 2,2-Bis(4-hydroxyphenyl)propane isespecially preferable among the above compounds.

The aromatic carbonic acid diester to be used in the melt polymerizationis an ester of an optionally substituted aryl group, aralkyl group,etc., having a carbon number of from 6 to 10. Concrete examples of theester are diphenyl carbonate, ditolyl carbonate,bis(chlorophenyl)carbonate, m-cresyl carbonate, dinaphthyl carbonate andbis(diphenyl)carbonate.

The amount of the above aromatic carbonic acid diester is 1.00 to 1.30mol, preferably 1.05 to 1.10 mol based on 1 mol of the aromaticdihydroxy compound.

In a melt-polymerization process, a polymerization catalyst is used forincreasing the polymerization speed in the case of producing apolycarbonate by the transesterification reaction of an aromaticdihydroxy compound with an aromatic carbonic acid diester.

The polymerization catalyst is composed of an alkali metal compoundand/or an alkaline earth metal compound as a main component and, as isnecessary, a nitrogen-containing basic compound as a subsidiarycomponent.

Examples of the alkali metal compound are sodium hydroxide, potassiumhydroxide, lithium hydroxide, sodium bicarbonate, potassium bicarbonate,lithium bicarbonate, sodium carbonate, potassium carbonate, lithiumcarbonate, sodium acetate, potassium acetate, lithium acetate, sodiumstearate, potassium stearate, lithium stearate, sodium salt, potassiumsalt or lithium salt of bisphenol A, sodium benzoate, potassium benzoateand lithium benzoate.

Examples of the alkaline earth metal compound are calcium hydroxide,barium hydroxide, magnesium hydroxide, strontium hydroxide, calciumbicarbonate, barium bicarbonate, magnesium bicarbonate, strontiumbicarbonate, calcium carbonate, barium carbonate, magnesium carbonate,strontium carbonate, calcium acetate, barium acetate, magnesium acetate,strontium acetate, calcium stearate, barium stearate, magnesium stearateand strontium stearate.

Examples of the nitrogen-containing basic compound aretetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide,trimethylamine, triethylamine, dimethylbenzylamine and triphenylamine.

The above polymerization catalysts may be used singly or in combination.

The amount of the polymerization catalyst is selected in the range offrom 1×10⁻⁸to 1×10⁻⁴ equivalent, preferably from 1×10⁻⁷ to 1×10⁻⁴equivalent, more preferably 1×10⁻⁶ to 5×10⁻⁵ equivalent in the case ofan alkali metal compound and/or an alkaline earth metal compound basedon 1 mol of the aromatic dihydroxy compound.

In the case of using a nitrogen-containing basic compound as asubsidiary component, its amount is selected within the range between1×10⁻⁵ and 1×10⁻³ equivalent, preferably 1×10⁻⁵ and 5×10⁻⁴ equivalentbased on 1 mol of the aromatic dihydroxy compound.

In the case of using an alkali metal compound and/or an alkaline earthmetal compound in combination with a nitrogen-containing basic compound,the total amount of both components is 1×10⁻⁸ to 1×10⁻³ equivalent,preferably 1×10⁻⁷ to 1×10⁻³ equivalent, more preferably 1×10⁻⁶ to 5×10⁻⁴equivalent based on 1 mol of the aromatic dihydroxy compound.

Other compounds may be used as cocatalysts as necessary in themelt-polymerization process. Conventional catalysts for esterificationreaction and transesterification reaction such as an alkali metal oralkaline earth metal salt of boron or aluminum hydroxide, a quaternaryammonium salt, an alkali metal or alkaline earth metal alkoxide, anorganic acid salt of an alkali metal or alkaline earth metal, a zinccompound, a boron compound, a silicon compound, a germanium compound, anorganic tin compound, a lead compound, an osmium compound, an antimonycompound and a zirconium compound can be used as the above cocatalystcompound, however, the cocatalyst is not restricted by the aboveexamples. The cocatalyst may be used singly or in combination of two ormore kinds of cocatalysts.

The melt-polymerization can be carried out by a conventional method byheating the reaction mixture in an inert gas atmosphere under stirringand distilling out the produced aromatic monohydroxy compound.

The reaction temperature is preferably in the range of from 120 to 350°C. in general. The vacuum degree of the system is increased to 10 to 0.1Torr at the later stage of the reaction to facilitate the distilling outof the produced aromatic monohydroxy compound to complete the reaction.

The polycarbonate to be used in the terminal-blocking reaction of thepresent invention may take any form such as a pellet form or a moltenform. A polycarbonate produced by melt-polymerization is generallysupplied continuously in molten state.

The intrinsic viscosity of the polycarbonate is preferably 0.3 or above.

The order of the terminal-blocking operation and the stabilizationoperation is extremely important in the present invention, and it isnecessary to carry out the terminal blocking, first, taking advantage ofthe reactivity of the hydroxy terminal groups of the polycarbonate whichcontains a still active polymerization catalyst after the meltpolycondensation and, thereafter, to add a stabilizer to the system toneutralise the catalytic activity and stabilize the polymer. Apolycarbonate resin having excellent thermal stability, color stabilityand hydrolysis resistance can be produced by this procedure.

If the stabilization operation is carried out before the terminalblocking operation after the melt-polycondensation, addition of anadditional catalyst becomes necessary for performing the terminalblocking operation. Furthermore, when the terminal-blocking reaction iscarried out after the stabilization operation, polycarbonate becomesactive again (because of the additional catalyst) and the obtainedpolycarbonate resin ends up with poor thermal stability, color stabilityand hydrolysis resistance unless an additional stabilization operationafter the terminal blocking operation follows according to the presentinvention.

The reactor for performing the terminal blocking operation in thepresent invention is preferably a twin-screw extruder, a horizontalreactor, a vertical stirring tank, etc. Use of a twin-screw extruder ispreferable because post-treatment such as addition of a stabilizer anddegassing (removal of gases and volatile substances) can be carried outsimultaneously with the terminal-blocking operation to achieve thesimplification of the process and the reduction of the apparatus cost.The horizontal reactor may be a single shaft horizontally-placed reactoror a double-shaft horizontal reactor.

A twin-screw extruder to perform the terminal blocking reaction ispreferably provided with unit process zones comprising a kneading partand a vent part. The extruder may have one or plural unit process zones.The kneading part is preferably placed at the upstream side of the ventpart based on the flowing direction of the polycarbonate. The kneadingpart is preferably directly connected to the vent part without a polymerseal part in between. When a polymer seal part is present between thekneading part and the vent part, the decomposition of polycarbonate mayoccur because the reaction by-products generated in the kneading partcannot be instantaneously removed from the system.

The terminal-blocking agent is preferably added at the kneading part ofthe unit process zone. The kneading part contains stirring blades suchas paddle-type blades usually called as kneading disks to performkneading of the polycarbonate and the terminal-blocking agent. Thefeeding port of the terminal-blocking agent at the kneading part ispreferably placed at its upstream side based on the flowing direction ofthe polycarbonate.

The vent part is preferably provided with a screw segment called as afull-flight segment having a polymer conveying function. A venting portis opened on the vent part and the vent part is preferably maintained ata reduced pressure by a vacuum pump, etc.

Omission of a polymer seal part between the kneading part and the ventpart enables maintaining at a reduced pressure the kneading part as wellas the vent part to facilitate instantaneous removal of the reactionby-products generated in the kneading part and suppress thedecomposition of the polycarbonate.

The temperature at the kneading of the polycarbonate with theterminal-blocking agent is from 200 to 350° C., preferably from 240 to320° C. When the temperature of the polycarbonate resin is lower than200° C., the kneading of the polycarbonate resin with theterminal-blocking agent becomes difficult. The temperature exceeding350° C. is also undesirable because accelerated dissipation of theterminal-blocking agent itself from the system lowers the reactivityremarkably and the polycarbonate is more liable to thermally decompose.

The pressure of the kneading process is 1,013 hPa (760 mmHg) or below,preferably 666 hPa (500 mmHg) or below. When the pressure exceeds 1,013hPa (760 mmHg), by-products generated by the terminal blocking reactioncannot be instantaneously removed from the system to cause undesirabledecomposition of polycarbonate.

The kneading time of the polycarbonate and the terminal-blocking agentis controllable by the average residence time of the polycarbonate inthe kneading part. In the case of an extruder having plural unit processzones, the kneading time is the sum of the residence times at the zones.

The kneading time is not shorter than 0.1 second. When the kneading timeis shorter than the above level, the kneading of the polycarbonate andthe terminal-blocking agent becomes difficult to retard the progress ofthe terminal-blocking reaction.

In the present invention, the resin is preferably evacuated at the ventpart under a pressure of 666 hPa (500 mmHg) or below for 0.1 second orlonger after kneading the terminal blocking agent. The evacuationtreatment is preferably carried out under a pressure lower than thepressure in the kneading of the terminal blocking agent. When thepressure at the vent part exceeds 666 hPa (500 mmHg), by-productsgenerated by the terminal blocking reaction cannot be removed from thesystem to possibly cause the decomposition of polycarbonate.

The evacuation period at the vent part can be controlled by the averageresidence time of the polycarbonate at the vent part. In the case of anextruder having plural unit process zones, the evacuation period isdefined as the sum of the periods at the individual zones. It ispreferably 0.1 second or longer. When the evacuation period is shorterthan the above level, generated by-products cannot be removed from thesystem to possibly cause the decomposition of the polycarbonate or causethe reaction by-products to remain in the produced polycarbonateresulting in the lowering of the quality of the polymer.

The terminal blocking agent to be used in the present invention is acompound expressed by the following formula (1).

[in the formula, R¹ is chlorine atom, a thoxycarbonyl group or anethoxycarbonyl group; R² is an alkyl group having a carbon number of 1to 30, an alkoxy group having a carbon number of 1 to 30, an aryl grouphaving a carbon number of 6 to 30 or an aryloxy group having a carbonnumber of 6 to 30, wherein the alkyl group having a carbon number of 1to 30 and the alkoxy group having a carbon number of 1 to 30 may bereplaced with methoxycarbonyl, ethoxycarbonyl, (o-oxycarbon and the arylgroup having a carbon number of 6 to 30 and the aryloxy group having acarbon number of 6 to 30 may be replaced with methoxycarbonyl,ethoxycarbonyl, (o-methoxycarbonylphenyl)oxycarbonyl,(o-ethoxycarbonylphenyl)oxycarbonyl, an alkyl having a carbon number of1 to 30 or an alkoxy having a carbon number of 1-30].

The compound to be used in the present invention and expressed by theabove formula (1) includes carbonates and carboxylic acid esters by thedefinition of the group R².

In the formula (1), R¹ is a chlorine atom, a methoxycarbonyl group(CH₃OCO—) or an ethoxycarbonyl group (C₂H₅OCO—). Among the above groups,a chlorine atom and a methoxycarbonyl group are preferable, and amethoxycarbonyl group is especially preferable.

The group R² is an alkyl group having a carbon number of 1 to 30, analkoxy group having a carbon number of 1 to 30, an aryl group having acarbon number of 6 to 30 or an aryloxy group having a carbon number of 6to 30.

The alkyl group having a carbon number of 1 to 30 may be astraight-chain group, a branched chain group or a cyclic group or mayhave an unsaturated group. Examples of such an alkyl group arestraight-chain alkyl groups such as methyl group, ethyl group, n-propylgroup, n-butyl group, n-pentyl group, n-hexyl group, n-octyl group,n-nonyl group, n-dodecanyl group, n-lauryl group, n-palmityl group orstearyl group, branched alkyl groups such as isopropyl group, t-butylgroup or 4-butylnonyl group, alkyl groups having unsaturated groups(alkenyl groups) such as allyl group, butenyl group, pentenyl group,hexenyl group, dodecenyl group or oleyl group, cycloalkyl groups such ascyclopentyl group or cyclohexyl group, etc. Long-chain alkyl groups,concretely lauryl group, stearyl group and dodecenyl group areespecially preferable among the above groups from the viewpoint of theimprovement of the mold releasability of the polymer.

The alkoxy group having a carbon number of 1 to 30 may be astraight-chain group, a branched chain group or a cyclic group or mayhave an unsaturated group. Examples of such alkoxy group arestraight-chain alkoxy groups such as methoxy group, ethoxy group,n-propoxy group, n-butoxy group, n-pentoxy group, n-hexoxy group,n-octoxy group, n-nonyloxy group, n-decanyloxy group, n-lauryloxy group,n-palmityloxy group or stearyloxy group, branched chain alkoxy groupssuch as iso-propoxy group, t-butyloxy group or 4-butylnonyloxy group,alkoxy groups having unsaturated groups such as allyloxy group,butenyloxy group, pentenyloxy group, hexenyloxy group, dodecenyloxygroup or oleyloxy group, cycloalkyloxy groups such as cyclopentyloxygroup or cyclohexyloxy group. Long-chain alkoxy groups such as lauryloxygroup, stearyloxy group and dodecenyloxy group are especially preferableamong the above groups from the viewpoint of the improvement of themold-releasability of the polymer.

The above alkyl group having a carbon number of 1 to 30 and alkoxy grouphaving a carbon number of 1 to 30 may be replaced with methoxycarbonyl,ethoxycarbonyl, (o-methoxycarbonylphenyl)-oxycarbonyl

The aryl group having a carbon number of 6 to 30 is, for example,phenyl, naphthyl, biphenyl and anthranyl.

The aryloxy group having a carbon number of 6 to 30 is, for example,phenoxy, naphthoxy, biphenyloxy and anthranyloxy.

These aryl groups having a carbon number of 6 to 30 and aryloxy groupshaving a carbon number of 6 to 30 may be replaced with methoxycarbonyl,ethoxycarbonyl, (o-methoxycarbonylphenyl)-oxycarbonyl,(o-ethoxycarbonylphenyl)-oxycarbonyl, an alkyl having a carbon number of1 to 30 or an alkoxy having a carbon number of 1 to 30. Same groups asthe above exemplified groups can be cited as examples of the alkylsubstituent having a carbon number of 1 to 30 and the alkoxy substituenthaving a carbon number of 1 to 30.

The compound expressed by the above formula (1) is categorized, based onthe definition of R², into carbonate compounds expressed by thefollowing formula (1)-1

and carboxylic acid aryl esters expressed by the following formula (1)-2

[wherein the definition of R¹ is the same as the formula (1); R²² is analkyl group having a carbon number of 1 to 30 or an aryl group having acarbon number of 6 to 30; these groups may be replaced with thesubstituents defined in the formula (1)].

Examples of the carbonate compounds expressed by the above formula (1)-1are 2-chlorophenyl aryl carbonates such as 2-chlorophenyl phenylcarbonate, 2-chlorophenyl 4′-methylphenyl carbonate, 2-chlorophenyl4′-ethylphenyl carbonate, 2-chlorophenyl 4′-n-butylphenyl carbonate,2-chlorophenyl 4′-t-butylphenyl carbonate, 2-chlorophenyl 4′-nonylphenylcarbonate, 2-chlorophenyl 4′-cumyl carbonate, 2-chlorophenyl naphthylcarbonate, 2-chlorophenyl 4′-methoxyphenyl carbonate, 2-chlorophenyl4′-ethoxyphenyl carbonate, 2-chlorophenyl 4′-n-butoxyphenyl carbonate,2-chlorophenyl 4′-t-butoxyphenyl carbonate, 2-chlorophenyl4′-nonyloxyphenyl carbonate, 2-chlorophenyl 4′-t-propyloxyphenylcarbonate, 2-chlorophenyl 2′-methoxycarbonylphenyl carbonate,2-chlorophenyl 4′-methoxy-carbonylphenyl carbonate, 2-chlorophenyl2′-ethoxycarbonylphenyl carbonate, 2-chlorophenyl4′-ethoxycarbonylphenyl carbonate, 2-chlorophenyl2′-(o-methoxycarbonylphenyl)oxycarbonylphenyl carbonate or2-chlorophenyl 2′-(o-ethoxycarbonylphenyl)oxycarbonylphenyl carbonate;

2-chlorophenyl alkyl carbonates such as 2-chlorophenyl methyl carbonate,2-chlorophenyl ethyl carbonate, 2-chlorophenyl n-butyl carbonate,2-chlorophenyl octyl carbonate, 2-chlorophenyl i-propyl carbonate,2-chlorophenyl 2-methoxycarbonylethyl carbonate, 2-chlorophenyl2-ethoxycarbonylethyl carbonate or 2-chlorophenyl2-(o-ethoxycarbonylphenyl)oxycarbonylethyl carbonate;

2-methoxycarbonylphenyl aryl carbonates such as 2-methoxy carbonylphenylphenyl carbonate, 2-methoxycarbonylphenyl methylphenyl carbonate,2-methoxycarbonylphenyl ethylphenyl carbonate, 2-methoxycarbonylphenylpropylphenyl carbonate, 2-methoxycarbonylphenyl n-butylphenyl carbonate,2-methoxy-carbonylphenyl t-butylphenyl carbonate,2-methoxycarbonylphenyl hexylphenyl carbonate, 2-methoxycarbonylphenylnonylphenyl carbonate, 2-methoxycarbonylphenyl dodecylphenyl carbonate,2-methoxycarbonylphenyl hexadecylphenyl carbonate,2-methoxycarbonylphenyl di-n-butylphenyl carbonate,2-methoxycarbonylphenyl di-t-butylphenyl carbonate,2-methoxycarbonylphenyl dinonylphenyl carbonate, 2-methoxycarbonylphenylcyclohexylphenyl carbonate, 2-methoxycarbonylphenyl naphthylphenylcarbonate, 2-methoxycarbonylphenyl biphenyl carbonate,2-methoxycarbonylphenyl cumylphenyl carbonate, 2-methoxycarbonylphenyl4′-methoxyphenyl carbonate, 2-methoxycarbonylphenyl 4′-ethoxyphenylcarbonate, 2-methoxycarbonylphenyl 4′-n-butoxyphenyl carbonate,2-methoxycarbonylphenyl 4′-t-butoxyphenyl carbonate,2-methoxycarbonylphenyl 4′-nonyloxyphenyl carbonate,2-methoxycarbonylphenyl 4′-cumyloxyphenyl carbonate,di(2-methoxycarbonylphenyl)carbonate, 2-methoxycarbonylphenyl4′-methoxycarbonylphenyl carbonate, 2-methoxycarbonylphenyl2′-ethoxycarbonylphenyl carbonate, 2-methoxycarbonylphenyl4′-ethoxycarbonylphenyl carbonate, 2-methoxycarbonylphenyl2′-(o-methoxycarbonylphenyl)oxycarbonylphenyl carbonate, or2-methoxycarbonylphenyl 2′-(o-ethoxycarbonylphenyl)oxycarbonylphenylcarbonate;

2-methoxycarbonylphenyl alkyl carbonates such as 2-methoxycarbonylphenylmethyl carbonate, 2-methoxycarbonylphenyl ethyl carbonate,2-methoxycarbonylphenyl n-butyl carbonate, 2-methoxycarbonylphenyl octylcarbonate, 2-methoxycarbonylphenyl nonyl carbonate,2-methoxycarbonylphenyl cetyl carbonate, 2-methoxycarbonylphenyl laurylcarbonate, 2-methoxycarbonylphenyl 2-methoxycarbonylethyl carbonate,2-methoxycarbonylphenyl 2-ethoxycarbonylethyl carbonate,2-methoxycarbonylphenyl 2-(o-methoxycarbonylphenyl)oxycarbonylethylcarbonate or 2-methoxycarbonylphenyl2-(o-ethoxycarbonylphenyl)oxycarbonylethyl carbonate;

2-ethoxycarbonylphenyl aryl carbonates such as 2-ethoxycarbonylphenylphenyl carbonate, 2-ethoxycarbonylphenyl methylphenyl carbonate,2-ethoxycarbonylphenyl ethylphenyl carbonate, 2-ethoxycarbonylphenylpropylphenyl carbonate, 2-ethoxycarbonylphenyl n-butylphenyl carbonate,2-ethoxycarbonylphenyl t-butylphenyl carbonate, 2-ethoxycarbonylphenylhexylphenyl carbonate, 2-ethoxycarbonylphenyl nonylphenyl carbonate,2-ethoxycarbonylphenyl dodecylphenyl carbonate, 2-ethoxycarbonyl-phenylhexadecylphenyl carbonate, 2-ethoxycarbonylphenyl di-n-butylphenylcarbonate, 2-ethoxycarbonylphenyl di-t-butylphenyl carbonate,2-ethoxycarbonylphenyl di-t-butylphenyl carbonate,2-ethoxycarbonylphenyl dinonylphenyl carbonate, 2-ethoxycarbonylphenylcyclohexylphenyl carbonate, 2-ethoxycarbonylphenyl naphthylphenylcarbonate, 2-ethoxycarbonylphenyl biphenyl carbonate,2-ethoxycarbonylphenyl cumylphenyl carbonate, 2-ethoxycarbonylphenyl4′-methoxyphenyl carbonate, 2-ethoxycarbonylphenyl 4′-ethoxyphenylcarbonate, 2-ethoxycarbonylphenyl 4′-n-butoxyphenyl carbonate,2-ethoxycarbonylphenyl 4′-t-butoxyphenyl carbonate,2-ethoxycarbonylphenyl 4′-nonyloxyphenyl carbonate,2-ethoxycarbonylphenyl 4′-cumyloxyphenyl carbonate,di(2-ethoxycarbonylphenyl)carbonate, 2-ethoxycarbonylphenyl4′-methoxycarbonylphenyl carbonate, 2-ethoxycarbonylphenyl4′-ethoxycarbonylphenyl carbonate, 2-ethoxycarbonylphenyl2′-(o-methoxycarbonylphenyl)oxycarbonylphenyl carbonate or2-ethoxycarbonylphenyl 2′-(o-ethoxycarbonylphenyl)oxycarbonylphenylcarbonate; and

2-ethoxycarbonylphenyl alkyl carbonates such as 2-ethoxycarbonylphenylmethyl carbonate, 2-ethoxycarbonylphenyl ethyl carbonate,2-ethoxycarbonylphenyl n-butyl carbonate, 2-ethoxycarbonylphenyl octylcarbonate, 2-ethoxycarbonylphenyl 2-methoxycarbonylethyl carbonate,2-ethoxycarbonylphenyl 2-ethoxycarbonylethyl carbonate,2-ethoxycarbonylphenyl 2-(o-methoxycarbonylphenyl)oxycarbonyl-ethylcarbonate or 2-ethoxycarbonylphenyl2-(o-ethoxycarbonylphenyl)oxycarbonylethyl carbonate.

Among the above compounds, 2-methoxycarbonylphenyl phenyl carbonate ispreferable because of its excellent hydrolysis resistance (wet-heatresistance) owing to the blocking of the terminal groups with phenylgroups.

Examples of the carboxylic acid aryl esters expressed by the aboveformula (1)-2 are aromatic carboxylic acid 2-chlorophenyl esters such as2-chlorophenyl benzoate, 2-chlorophenyl 4-methylbenzoate, 2-chlorophenyl4-ethylbenzoate, 2-chlorophenyl 4-n-butylbenzoate, 2-chlorophenyl4-t-butylbenzoate, 2-chlorophenyl 4-nonylbenzoate, 2-chlorophenyl4-cumylbenzoate, 2-chlorophenyl naphthoate, 2-chlorophenyl4-methoxybenzoate, 2-chlorophenyl 4-ethoxybenzoate, 2-chlorophenyl4-n-butoxybenzoate, 2-chlorophenyl 4-t-butoxybenzoate, 2-chlorophenyl4-nonyloxybenzoate, 2-chlorophenyl 4-cumyloxybenzoate, 2-chlorophenyl2-methoxycarbonylbenzoate, 2-chlorophenyl 4-methoxycarbonyl-benzoate,2-chlorophenyl 2-ethoxycarbonylbenzoate, 2-chlorophenyl4-ethoxycarbonylbenzoate, 2-chlorophenyl2-(o-methoxycarbonyl-phenyl)oxycarbonylbenzoate or 2-chlorophenyl2-(o-ethoxycarbonyl-phenyl)oxycarbonylbenzoate;

aliphatic carboxylic acid 2-chlorophenyl esters such as 2-chlorophenylacetate, 2-chlorophenyl propionate, 2-chlorophenyl valerate,2-chlorophenyl pelargonate, 2-chlorophenyl 1-methylpropionate,2-chlorophenyl 2-methoxycarbonylpropionate, 2-chlorophenyl2-ethoxycarbonylbutyrate, 2-chlorophenyl4′-(2-methoxycarbonylphenyl)oxycarbonylbutyrate or 2-chlorophenyl4′-(2-methoxycarbonylphenyl)oxycarbonylbutyrate;

aromatic carboxylic acid (2′-methoxycarbonylphenyl)esters such as(2-methoxycarbonylphenyl)benzoate, 2′-methoxy-carbonylphenyl4-methylbenzoate, 2′-methoxycarbonylphenyl 4-ethylbenzoate,2′-methoxycarbonylphenyl 4-n-butylbenzoate, 2′-methoxycarbonylphenyl4-t-butylbenzoate, 2′-methoxycarbonyl-phenyl naphthoate,2′-methoxycarbonylphenyl 4-nonylbenzoate, 2′-methoxycarbonylphenyl4-cumylbenzoate, 2′-methoxycarbonyl-phenyl 4-methoxybenzoate,2′-methoxycarbonylphenyl 4-ethoxybenzoate, 2′-methoxycarbonylphenyl4-n-butoxybenzoate, 2′-methoxycarbonylphenyl 4-t-butoxybenzoate,2′-methoxycarbonyl-phenyl 4-cumyloxybenzoate, 2′-methoxycarbonylphenyl2-methoxycarbonylbenzoate, 2′-methoxycarbonylphenyl4-methoxy-carbonylbenzoate, 2′-methoxycarbonylphenyl4-ethoxycarbonylbenzoate, 2′-methoxycarbonylphenyl3-(o-methoxycarbonylphenyl)oxycarbonylbenzoate, 2′-methoxycarbonylphenyl4-(o-methoxycarbonylphenyl)oxycarbonylbenzoate or(2′-methoxycarbonyl)phenyl3-(o-ethoxycarbonylphenyl)oxycarbonylbenzoate; and

aromatic carboxylic acid 2′-ethoxycarbonylphenyl esters such as2-ethoxycarbonylphenyl benzoate, 2′-ethoxycarbonyl-phenyl4-methylbenzoate, 2′-ethoxycarbonylphenyl 4-ethylbenzoate,2′-ethoxycarbonylphenyl 4-n-butylbenzoate, 2′-ethoxycarbonylphenyl4-t-butylbenzoate, 2′-ethoxycarbonylphenyl naphthoate,2′-ethoxycarbonylphenyl 4-nonylbenzoate, 2′-ethoxycarbonylphenyl4-cumylbenzoate, 2′-ethoxycarbonylphenyl 4-methoxybenzoate,2′-ethoxycarbonylphenyl 4-ethoxybenzoate, 2′-ethoxycarbonylphenyl4-n-butoxybenzoate, 2′-ethoxycarbonylphenyl 4-t-butoxybenzoate,2′-ethoxycarbonylphenyl 4-nonyloxybenzoate, 2′-ethoxycarbonyl-phenyl4-cumyloxybenzoate, 2′-ethoxycarbonylphenyl 2-methoxycarbonylbenzoate,2′-ethoxycarbonylphenyl 4-ethoxycarbonyl-benzoate,2′-ethoxycarbonylphenyl 3-(o-methoxycarbonylphenyl)oxycarbonylbenzoate,2′-ethoxycarbonylphenyl 4-(o-methoxycarbonyl-phenyl)oxycarbonylbenzoateor 2′-ethoxycarbonylphenyl3-(o-methoxycarbonylphenyl)oxycarbonylbenzoate.

Especially preferable compounds expressed by the formula (1) are2-methoxycarbonylphenyl benzoate, 2′-methoxycarbonylphenyl4-cumylbenzoate, 2-ethoxycarbonylphenyl benzoate and2′-methoxycarbonylphenyl 4-(o-methoxycarbonylphenyl)oxycarbonylbenzoate.

The above-mentioned terminal-blocking agent is added in an amount of 0.3to 4 mol-equivalent based on the hydroxyl terminal group amount of thepolycarbonate. More preferably, the addition amount is 0.5 to 1.5mol-equivalent. Sufficient terminal-blocking effect cannot be attainedwhen the addition amount of the terminal-blocking agent is less than 0.3mol-equivalent, and the addition of more than 4 mol-equivalent of theagent is unfavorable because of the lowering of quality caused by theexcess agent remaining in the polycarbonate.

For a reactor having plural unit process zones, the sum of the additionamounts of the terminal-blocking agent in individual zones is preferablyadjusted to be fallen within the above range.

The present invention enables suppression of the decomposition ofpolycarbonate caused by the reaction by-products, easy control of theintrinsic viscosity of the polycarbonate resin and quick completion ofthe terminal blocking reaction to produce a terminal-blockedpolycarbonate by adopting the above-mentioned temperature conditions,pressure conditions and kneading time in the kneading part, the pressureconditions and evacuation period in the vent part and further the kindand the addition amount of the terminal-blocking agent.

The above-mentioned terminal blocking reaction conditions are notrestricted to the case of using a twin-screw extruder as the terminalblocking reactor but applicable to a horizontal reactor or a verticalstirring tank reactor.

In the above-mentioned process for producing a polycarbonate resinhaving low hydroxy-terminal content by the reaction of a polycarbonatewith a terminal-blocking agent, a polycarbonate resin having furtherexcellent thermal stability, color stability and hydrolysis resistancecan be produced by adding a stabilizer to deactivate the catalystsubsequent to the terminal blocking operation.

Conventional stabilizers are effectively usable as the stabilizer, andamong others, sulfonic acid ammonium salts, sulfonic acid phosphoniumsalts and sulfonic acid esters are preferable.

In addition to the above, esters, ammonium salts and phosphonium saltsof dodecylbenzenesulfonic acid, and esters, ammonium salts andphosphonium salts of p-toluenesulfonic acid and esters, ammonium saltsand phosphonium salts of benzenesulfonic acid may be used as thestabilizer.

Especially preferable compounds among the above compounds arededecylbenzenesulfonic acid tetrabutylphosphonium salt andp-toluenesulfonic acid tetrabutylammonium salt.

Preferable examples of the sulfonic acid esters are methylbenzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate, octylbenzenesulfonate, phenyl benzenesulfonate, methyl p-toluenesulfonate,ethyl p-toluenesulfonate, butyl p-toluenesulfonate, octylp-toluenesulfonate and phenyl p-toluenesulfonate.

The amount of the stabilizer to be added to a polycarbonate produced bymelt-polymerization is 0.5 to 50 mol, preferably 0.5 to 10 mol, morepreferable 0.8 to 5 mol based on 1 mol of the above-mentioned mainpolycondensation catalyst selected from alkali metal compounds andalkaline earth metal compounds. The amount usually corresponds to 0.01to 500 ppm based on the polycarbonate.

The addition and kneading of the stabilizer are preferably carried outby using a twin-screw extruder provided with unit process zones each ofwhich comprises a kneading part and a vent part with or without apolymer seal part in between. The number of the unit process zones maybe one or plural.

The stabilizer can be added to the kneading part directly and/or in theform of a solution. A stirring blade such as a paddle blade is placed inthe kneading part to perform the kneading of the polycarbonate with thestabilizer. The kneading part can be placed upstream of the vent part.

The vent part has a vent hole and the inside of the vent part may bemaintained under a reduced pressure with a vacuum pump, etc.

The kneading of the polycarbonate and the stabilizer is carried out at200 to 350° C., preferably 240 to 320° C. under a pressure of 1.333×10⁵hPa (105 mmHg) or below, preferably 1.333×10⁴ hPa (10⁴ mmHg) or belowfor 0.1 second or longer. The kneading at a temperature lower than 200°C. causes difficulty in the kneading of the polycarbonate and thestabilizer, and unfavourable thermal decomposition of polycarbonatetakes place by the kneading at a temperature above 350° C. The kneadingpressure exceeding 1.333×10⁵ hPa (10⁵ mmHg) is also unfavorable owing tothe problem of the pressure resistance of the reactor.

The addition of the stabilizer in the form of a solution is preferablebecause the solvent acts as a degassing assistant to effectivelyaccelerate removal of volatile impurities. It is also useful to placeanother unit process zone comprising a kneading part and a vent partafter a unit process zone or unit process zones for the addition of thestabilizer and adding a liquid (e.g. water) which can act as a degassingassistant to the additional unit process zone.

Solvents and volatile impurities can be removed from the system byevacuating the vent part with a vacuum pump, etc. The evacuation iscarried out at a pressure of 1,013 hPa (760 mmHg) or below, preferably666 hPa (500 mmHg) or below for 0.1 seconds or longer. The vent partpressure exceeding 1,013 hPa (760 mmHg) may cause difficulty in removingthe added solvents and the volatile impurities from the system.

Water, saturated aliphatic hydrocarbons and aromatic hydrocarbons arepreferably used as the solvent for the addition and kneading of thestabilizer in the present invention.

The saturated aliphatic hydrocarbon to be used in the process has aboiling point of preferably 30 to 270° C., more preferably 50 to 200°C., and still more preferably 50 to 150° C. under the atmosphericpressure.

Examples of the saturated aliphatic hydrocarbons are 2-methylbutane,pentane, 2,2-dimethylbutane, 2,3-dimethylbutane, hexane,2-methylpentane, 3-methylpentane, 2,2-dimethylpentane,2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, heptane,2-methylhexane, 3-methylhexane, 2,2,3-trimethylbutane,2,2-dimethylhexane, 2,5-dimethylhexane, 3,4-dimethylhexane,hexamethylethane, 2-methylheptane, 4-methylheptane, octane,2,2,4-trimethylpentane, 2,3,4-trimethylpentane, nonane, decane,undecane, dodecane, tridecane, tetradecane and 1-pentadecane.

The aromatic hydrocarbon has a boiling point of preferably 80 to 270°C., more preferably 80 to 200° C. and still more preferably 80 to 150°C. under the atmospheric pressure.

Examples of the aromatic hydrocarbons are benzene, toluene, o-xylene,m-xylene, p-xylene, ethylbenzene, 2-ethyltoluene, 3-ethyltoluene,4-ethyltoluene, cumene, mesitylene, propylbenzene,1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, butylbenzene,sec-butylbenzene, tert-butylbenzene, o-cymene, m-cymene, p-cymene,1,2-diethylbenzene, 1,4-diethylbenzene, 1,2,3,5-tetramethylbenzene,1,2,4,5-tetramethylbenzene, amylbenzene, 4-tert-butyltoluene,(2,2-dimethylpropyl)benzene, isoamylbenzene, 5-tert-butyl-m-xylene,1,3-diisopropylbenzene, 1,4-diisopropylbenzene, 1-phenylhexane,1,2,4-trimethylbenzene and 1,3-di-tert-butylbenzene.

Even if the above terminal-blocking agent and/or stabilizer contain avolatile compound or generate a thermal decomposition product throughthermal decomposition, these substances can be removed together with thesolvents and the volatile impurities by the evacuation treatment.

The polycarbonate to be used in the addition and kneading of thestabilizer in the present invention may take any form such as pelletform or molten form. A polycarbonate produced by melt-polymerization isgenerally supplied continuously in molten state.

The terminal-blocking agent and the stabilizer to be added to the systemmay have any form such as solid, powder or liquid. The environment ofthe additives may be an ordinary atmosphere, however, when thedeterioration of quality is to be especially avoided, it is alsorecommended to replace the atmosphere beforehand with an inert gas suchas nitrogen or argon or, if the additives are in the form of a solution,bubbling (sparging) the solution with an inert gas.

The material of the equipments to perform the melt-polycondensation ofthe polycarbonate, the addition and kneading of the terminal-blockingagent and the addition and kneading of the stabilizer is preferably ametallic material selected from stainless steel, nickel, nickel alloy,titanium, titanium alloy and steel, and the material for the partcontacting with the polymer is preferably stainless steel or steelhaving nickel coating layer, titanium alloy coating layer or chromiumcoating layer. Use of materials other than the above materials may causedeactivation of the polycondensation catalyst, delay in polymerizationof polycarbonate or the terminal blocking reaction or discoloring of thepolycarbonate.

The stainless steel to be used in the present invention is, for example,SUS201, SUS202, SUS301, SUS302, SUS302E, SUS303, SUS303Se, SUS304,SUS304L, SUS305, SUS308, SUS308L, SUS309, SUS309S, SUS309Mo, SUS310,SUS310S, SUS312, SUS316, SUS316L, SUS317, SUS317L, SUS318, SUS321,SUS327, SUS329, SUS330, SUS347, SUS384, SUS385, SUS403, SUS405, SUS410,SUS416, SUS420, SUS420F, SUS429, SUS430, SUS430F, SUS431, SUS434,SUS440A, SUS440B, SUS440C, SUS440F, SUS446, SUS630, SUS631 and SUS661.

Examples of the nickel and the nickel alloys are pure nickel metal, lowcarbon nickel (NLC), nickel-aluminum-titanium alloy (ND),nickel-chromium-boron-silicon alloy, Monel metal, Monel K-500, Monel400, K Monel, S Monel, Hastelloy A, Hastelloy B, Hastelloy C, HastelloyD, Hastelloy F, Nichrome, Incoloy, Incoloy 800, Inconel 600, Inconel625, Inconel 718, Inconel X, Illium G, Ni-O-Nel, Carpenter 20 andworsite.

Examples of the titanium and the titanium alloys are pure titaniummetal, titanium plate (TP35), titanium-palladium alloy, titanium nitrideand titanium carbide.

Examples of the steel are SS34, SS41, SS50 and SS55 as steel for generalstructural purpose, SKD-11 as alloy tool steel, SM-41, SM-50, SM-50Y,SM-53 and SM-58 as steel with improved weatherability and SUH309 andSUH409 as heat-resisting steel.

The above abbreviations such as SUS201, SS34, etc. are notations of JISspecifications.

The above stainless steel, nickel, nickel alloy, titanium, titaniumalloy and steel are preferably subjected as necessary to variousheat-treatment such as burn-in, annealing, hardening, tempering,cementation, nitriding, sulfurization and supzero treatment to improvethe strength.

A lining structure (double-layer structure) using two or more kinds ofmaterials selected from the above materials may be adopted in thereactor to be used in the present invention. A hard metallic materialhaving excellent abrasion resistance and corrosion resistance has to beused at the part contacting with the polymer.

Stainless steels or steels having nickel coating layer, titanium alloycoating layer or chromium coating layer may be used at the partcontacting with the polymer.

In the case of using the above-mentioned coated metal, it is preferableto apply various heat-treatment such as burn-in, annealing, hardening,tempering, cementation, nitriding, sulfurization and supzero treatmentto improve the strength.

Although there is no particular restriction on the kind of the stainlesssteel or steel to be used in the coating, use of the above-mentionedstainless steels and steels is preferable.

Decomposition of polycarbonate by the by-product of terminal blockingreaction, a problem inherent to conventional process, was suppressed andthe intrinsic viscosity of the finally produced polycarbonate resinbecame easily controllable by the use of this process for the productionof polycarbonate resin.

A polycarbonate resin containing a limited number of hydroxy terminalsand having excellent thermal stability, color stability and hydrolysisresistance can be produced by the process of the present invention. Themolded article of the produced polycarbonate resin has remarkablyimproved quality.

EFFECT OF THE INVENTION

A polycarbonate resin containing a limited number of hydroxy terminalsand having excellent thermal stability, color stability and hydrolysisresistance can be produced according to the process of the presentinvention, wherein, in the process of the melt-polycondensation of anaromatic dihydroxy compound with an aromatic carbonic acid diester inthe presence of a polycondensation catalyst, a terminal-blocking agentis added and kneaded into the system under a reduced pressure after themelt-polycondensation reaction followed by the addition of a stabilizerto the kneaded mixture.

EXAMPLES

The present invention is described by the following Examples. Thephysical properties, etc. of the polycarbonate in the following Exampleswere measured by the following methods.

The intrinsic viscosity was measured by using a methylene chloridesolution of a polycarbonate having a concentration of 0.7 g/dl at 20° C.with a Ubbellohde viscometer.

The color of pellet was determined by using a color-difference meterND-1001DP manufactured by Nihon Denshoku Ind. Co., measuring the Labvalues by the reflection method and using the b value as a measure ofyellowness.

The amount of terminal hydroxyl group in the polycarbonate resin wasdetermined by dissolving 0.02 g of a specimen in 0.4 ml of chloroformand determining the value at 20° C. by using 1H-NMR (EX-270, product ofJEOL Ltd.)

Example 1

Diphenyl carbonate and 2,2-bis(4-hydroxyphenyl)propane were charged intoa melting tank furnished with a stirrer at a ratio of 1.05 mol of theformer per 1 mol of the latter, the atmosphere in the tank was replacedwith nitrogen and the content of the tank was melted at 150° C.

The molten mixture was transferred to a vertical stirring tank furnishedwith a fractionation column, added with 2×10⁻⁶ equivalent of bisphenol Adisodium salt and 1×10⁻⁴ equivalent of tetramethylammonium hydroxidebased on 1 mol of 2,2-bis(4-hydroxyphenyl)propane and reacted with eachother while keeping the system at a reaction temperature of 180° C. anda reaction pressure of 133.3 hPa (100 mmHg) and removing the producedphenol through the fractionation column, and subsequently the reactionmixture was subjected to prepolymerization at a reaction temperature of200° C. under a reaction pressure of 40.0 hPa (30 mmHg).

The prepolymerized polymer was transferred to a vertical stirring tankwithout fractionation column and maintained at 270° C. and 1.333 hPa (1mmHg) to produce a polycarbonate with the targeted intrinsic viscosityof 0.35 and the whole quantity of the produced polycarbonate waspelletized. SUS316 was used as the material of the melting tank and thevertical stirring tank.

The obtained pellet had an intrinsic viscosity of 0.354, a b-value ofthe Lab color system of 0.3 and a terminal hydroxyl group content of 100mol/ton.

The produced polycarbonate pellets were supplied to a twin-screwextruder having an inner diameter of 30 mm, provided with three-stageaddition ports with three-stage vent holes, having an extrusion capacityof 5 kg/hr and operated at a rotational speed of 200 rpm, added with 1.5mol-equivalent of 2-methoxycarbonylphenyl phenyl carbonate based on thehydroxy terminal group amount of the polycarbonate and subjected toterminal blocking reaction under the conditions shown in the Table 1.

Thereafter, dodecylbenzenesulfonic acid tetrabutyl-phosphonium salt wasadded as a stabilizer to the twin-screw extruder in the form of anaqueous solution and kneaded into the polycarbonate. The addition andkneading of the stabilizer was carried out at an addition amount of 20ppm based on the polycarbonate at an extrusion rate of 5 kg/hr, arotational speed of 200 rpm, a resin temperature of 290° C., a kneadingpressure of 1.333×10⁴ hPa (10⁴ mmHg), a kneading time of 20 seconds, avent-part pressure of 20.0 hPa (15 mmHg) and a venting period of 20seconds and using a single unit process zone.

The whole quantity of the polycarbonate resin produced by the aboveproduction process was pelletized.

The material of the twin-screw extruder used in the terminal-blockingreaction and the addition and kneading of the stabilizer was anickel-chromium-boron-silicon alloy for the inner face of the cylinderand SKD-11 having titanium nitride coating layer for the screw segment.

The measured results of the amount of hydroxy terminal, the intrinsicviscosity and the b-value of the Lab color system of the finallyobtained polycarbonate resin are shown in the Table 1.

TABLE 1 Terminal Blocking Example 1 Reaction Reactor Twin Screw ExtruderTerminal Blocking Agent

Amount of the Blocking Agent (mol-equiv) 1.5 No. of Unit Process Zones 2Resin Temp. (° C.) 290 Kneading Part Pressure (mmHg) 100 Reaction Time(sec) 20 Vent Part Pressure (mmHg) 5 Reaction Time (sec) 20 ExperimentalIntrinsic Viscosity 0.347 Result b-Value of the Lab Color System 1.3Amount of Hydroxy Terminal (mol/ton) 18

Examples 2 to 15

Polycarbonate resins were produced under the conditions of the Example 1except for the terminal-blocking reaction performed under the conditionsshown in the Tables 2 to 8 and the whole quantity of the produced resinswere pelletized.

The measured results of the amount of hydroxy terminal, the intrinsicviscosity and the b-value of the Lab color system of the finallyobtained polycarbonate resins are shown in the Tables 2 to 8.

TABLE 2 Terminal Blocking Example 2 Example 3 Reaction Reactor TwinScrew Extruder Twin Screw Extruder Terminal Blocking Agent

Amount of the Agent (mol-equivalent) 0.5 4 No. of Unit Process Zones 2 2Resin Temp. (° C.) 290 290 Kneading Part Pressure (mmHg) 100 100Reaction Time (sec) 20 20 Vent Part Pressure (mmHg) 5 5 Reaction Time(sec) 20 20 Experimental Intrinsic Viscosity 0.352 0.345 Results b-Valueof the Lab Color System 1.2 1.4 Amount of Hydroxy Terminal (mol/ton) 579

TABLE 3 Terminal Blocking Example 4 Example 5 Reaction Reactor TwinScrew Extruder Twin Screw Extruder Terminal Blocking Agent

Amount of the Agent (mol-equivalent) 1.5 1.5 No. of Unit Process Zones 31 Resin Temp. (° C.) 290 290 Kneading Part Pressure (mmHg) 100 100Reaction Time (sec) 30 10 Vent Part Pressure (mmHg) 5 5 Reaction Time(sec) 30 10 Experimental Intrinsic Viscosity 0.350 0.349 Results b-Valueof the Lab Color System 1.3 1.3 Amount of Hydroxy Terminal (mol/ton) 531

TABLE 4 Terminal Blocking Example 6 Example 7 Reaction Reactor TwinScrew Extruder Twin Screw Extruder Terminal Blocking Agent

Amount of the Agent (mol-equivalent) 1.5 1.5 No. of Unit Process Zones 22 Resin Temp. (° C.) 290 290 Kneading Part Pressure (mmHg) 760 7Reaction Time (sec) 20 20 Vent Part Pressure (mmHg) 5 5 Reaction Time(sec) 20 20 Experimental Intrinsic Viscosity 0.350 0.353 Results b-Valueof the Lab Color System 1.2 1.3 Amount of Hydroxy Terminal (mol/ton) 1525

TABLE 5 Terminal Blocking Example 8 Example 9 Reaction Reactor TwinScrew Extruder Twin Screw Extruder Terminal Blocking Agent

Amount of the Agent (mol-equivalent) 1.5 1.5 No. of Unit Process Zones 22 Resin Temp. (° C.) 290 290 Kneading Part Pressure (mmHg) 100 100Reaction Time (sec) 300 20 Vent Part Pressure (mmHg) 5 5 Reaction Time(sec) 20 300 Experimental Intrinsic Viscosity 0.348 0.353 Resultsb-Value of the Lab Color System 1.5 1.0 Amount of Hydroxy Terminal(mol/ton) 17 10

TABLE 6 Terminal Blocking Example 10 Example 11 Reaction Reactor TwinScrew Extruder Twin Screw Extruder Terminal Blocking Agent

Amount of the Agent (mol-equivalent) 1.5 1.5 No. of Unit Process Zones 22 Resin Temp. (° C.) 290 290 Kneading Part Pressure (mmHg) 100 100Reaction Time (sec) 20 20 Vent Part Pressure (mmHg) 1 100 Reaction Time(sec) 20 20 Experimental Intrinsic Viscosity 0.351 0.345 Results b-Valueof the Lab Color System 1.1 1.4 Amount of Hydroxy Terminal (mol/ton) 1825

TABLE 7 Terminal Blocking Example 12 Example 13 Reaction Reactor TwinScrew Extruder Twin Screw Extruder Terminal Blocking Agent

Amount of the Agent (mol-equivalent) 1.5 1.5 No. of Unit Process Zones 22 Resin Temp. (° C.) 250 315 Kneading Part Pressure (mmHg) 100 100Reaction Time (sec) 20 20 Vent Part Pressure (mmHg) 5 5 Reaction Time(sec) 20 20 Experimental Intrinsic Viscosity 0.348 0.346 Results b-Valueof the Lab Color System 1.1 1.4 Amount of Hydroxy Terminal (mol/ton) 1920

TABLE 8 Terminal Blocking Example 14 Example 15 Reaction Reactor TwinScrew Extruder Twin Screw Extruder Terminal Blocking Agent

Amount of the Agent (mol-equivalent) 1.5 0.8 No. of Unit Process Zones 21 Resin Temp. (° C.) 290 290 Kneading Part Pressure (mmHg) 100 100Reaction Time (sec) 20 10 Vent Part Pressure (mmHg) 5 5 Reaction Time(sec) 20 10 Experimental Intrinsic Viscosity 0.345 0.349 Results b-Valueof the Lab Color System 1.5 1.2 Amount of Hydroxy Terminal (mol/ton) 314

Example 16

A polycarbonate resin was produced under the conditions of the Example 1except for the terminal-blocking reaction performed by using ahorizontal reactor (made of SUS316) at an extrusion rate of 20 kg/hr anda rotational speed of 10 rpm under conditions shown in the Table 9 andthe whole quantity of the produced resin was pelletized.

The measured results of the amount of hydroxy terminal, the intrinsicviscosity and the b-value of the Lab color system of the finallyobtained polycarbonate resins are shown in the Table 9.

TABLE 9 Terminal Blocking Example 16 Reaction Reactor Double ShaftHorizontal Reactor Terminal Blocking Agent

Amount of the Blocking Agent (mol-equiv) 1.0 No. of Unit Process Zones 1Resin Temp. (° C.) 270 Kneading Part Pressure (mmHg) 760 Reaction Time(sec) 60 Vent Part Pressure (mmHg) 1 Reaction Time (sec) 3600Experimental Intrinsic Viscosity 0.355 Result b-Value of the Lab ColorSystem 1.2 Amount of Hydroxy Terminal (mol/ton) 9

Example 17

A polycarbonate resin was produced under the conditions of the Example 1except for the terminal-blocking reaction performed by using a singleshaft horizontal reactor (made of SUS316) at an extrusion rate of 20kg/hr and a rotational speed of 10 rpm under conditions shown in theTable 10 and the whole quantity of the produced resin was pelletized.

The measured results of the amount of hydroxy terminal, the intrinsicviscosity and the b value of the Lab color system of the finallyobtained polycarbonate resins are shown in the Table 10.

TABLE 10 Terminal Blocking Example 17 Reaction Reactor Single ShaftHorizontal Reactor Terminal Blocking Agent

Amount of the Blocking Agent (mol-equiv) 1.0 No. of Unit Process Zones 1Resin Temp. (° C.) 270 Kneading Part Pressure (mmHg) 1 Reaction Time(sec) 0.1 Vent Part Pressure (mmHg) 1 Reaction Time (sec) 2400Experimental Intrinsic Viscosity 0.353 Result b-Value of the Lab ColorSystem 1.3 Amount of Hydroxy Terminal (mol/ton) 21

Example 18

Diphenyl carbonate and 2,2-bis(4-hydroxyphenyl)propane were charged intoa melting tank furnished with a stirrer at a ratio of 1.05 mol of theformer per 1 mol of the latter, the atmosphere in the tank was replacedwith nitrogen and the content of the tank was melted at 150° C.

The molten mixture was transferred to a vertical stirring tank furnishedwith a fractionation column, added with 2×10⁻⁶ equivalent of bisphenol Adisodium salt and 1×10⁻⁴ equivalent of tetramethylammonium hydroxidebased on 1 mol of 2,2-bis(4-hydroxyphenyl)propane and reacted with eachother while keeping the system at a reaction temperature of 180° C. anda reaction pressure of 133.3 hPa (100 mmHg) and removing the producedphenol through the fractionation column, and subsequently the reactionmixture was subjected to prepolymerization at a reaction temperature of200° C. under a reaction pressure of 40.0 hPa (30 mmHg).

The prepolymerized polymer was transferred to a vertical stirring tankwithout a fractionation column and maintained at 270° C. and 1.333 hPa(1 mmHg) to produce a polycarbonate with the targeted intrinsicviscosity of 0.35.

2-Methoxycarbonylphenyl phenyl carbonate was added as aterminal-blocking agent to the vertical stirring tank in an amount of1.0 mol-equivalent based on the hydroxy terminal group amount of thepolycarbonate, the terminal blocking reaction was carried out under theaddition kneading conditions shown in the Table 11, and the wholequantity of the produced polycarbonate was pelletized.

The produced polycarbonate pellets were supplied to a twin-screwextruder having an inner diameter of 30 mm and provided with three-stageaddition ports with three-stage vent holes, and dodecylbenzenesulfonicacid tetrabutylphosphonium salt was added as a stabilizer to thekneading part of the twin-screw extruder in the form of an aqueoussolution and kneaded into the polycarbonate. The addition and kneadingof the stabilizer was carried out at an addition amount of 20 ppm basedon the polycarbonate at an extrusion rate of 5 kg/hr, a rotational speedof 200 rpm, a kneading pressure of 1.333×10⁴ hPa (10⁴ mmHg), a kneadingtime of 20 seconds, a vent-part pressure of 20.0 hPa (15 mmHg) and aventing period of 20 seconds.

The whole quantity of the polycarbonate resin produced by the aboveproduction process was pelletized.

The material of the twin-screw extruder used in the addition andkneading of the stabilizer was a nickel-chromium-boron-silicon alloy forthe inner face of the cylinder and SKD-11 having titanium nitridecoating layer for the screw segment.

The measured results of the amount of hydroxy terminal, the intrinsicviscosity and the b-value of the Lab color system of the finallyobtained polycarbonate resin are shown in the Table 11.

TABLE 11 Terminal Blocking Example 18 Reaction Reactor Vertical StirringTank Terminal Blocking Agent

Amount of the Blocking Agent (mol-equiv) 1.0 No. of Unit Process Zones 1Resin Temp (° C.) 270 Kneading Part Pressure (mmHg) 100 Reaction Time(sec) 600 Vent Part Pressure (mmHg) 1 Reaction Time (sec) 1200Experimental Intrinsic Viscosity 0.355 Result b-Value of the Lab ColorSystem 0.8 Amount of Hydroxy Terminal (mol/ton) 10

Examples 19 to 24

Polycarbonate resins were produced under the conditions of the Example 1except for the addition and kneading of the stabilizer performed underthe conditions shown in the Tables 12 to 14, and the whole quantity ofthe produced resins were pelletized.

The measured results of the amount of hydroxy terminal, the intrinsicviscosity and the b-value of the Lab color system of the finallyobtained polycarbonate resins are shown in the Tables 12 to 14.

TABLE 12 Example 19 Example 20 Addition and Reactor Twin Screw ExtruderTwin Screw Extruder Kneading of Stabilizer Extrusion Rate (kg/hr)  5  5Rotational Speed (rpm) 200  200  Stabilizer Dodecylbenzenesulfonic acidDodecylbenzenesulfonic acid tetrabutylphosphonium salttetrabutylphosphonium salt Adding Form of Stabilizer Aqueous SolutionAqueous Solution Amount of Stabilizer (ppm) 20 20 No. of Unit ProcessZones  1  1 Resin Temp. (° C.) 250  315  Kneading Part Pressure (mmHg) 10⁴  10⁴ Reaction Time (sec) 20 20 Vent Part Pressure (mmHg) 15 15Reaction Time (sec) 20 20 Experimental Intrinsic Viscosity    0.351   0.346 Result b-Value of the Lab Color System   1.0   1.5 Amount ofHydroxy Terminal (mol/ton) 22 18

TABLE 13 Example 21 Example 22 Addition and Reactor Twin Screw ExtruderTwin Screw Extruder Kneading of Stabilizer Extrusion Rate (kg/hr)  5  5Rotational Speed (rpm) 200  200  Stabilizer Dodecylbenzenesulfonic acidDodecylbenzenesulfonic acid tetrabutylphosphonium salttetrabutylphosphonium salt Adding Form of Stabilizer Aqueous SolutionUndiluted Stock Liquid Amount of Stabilizer (ppm) 20 20 No. of UnitProcess Zones  1  1 Resin Temp. (° C.) 290  290  Kneading Part Pressure(mmHg) 760  760  Reaction Time (sec) 20 20 Vent Part Pressure (mmHg) 1515 Reaction Time (sec) 20 20 Experimental Intrinsic Viscosity    0.351   0.348 Result b-Value of the Lab Color System   1.1   1.3 Amount ofHydroxy Terminal (mol/ton) 20 17

TABLE 14 Example 23 Example 24 Addition and Reactor Twin Screw ExtruderTwin Screw Extruder Kneading of Stabilizer Extrusion Rate (kg/hr)  5  5Rotational Speed (rpm) 200  200  Stabilizer p-Toluenesulfonic acid Butylp-toluenesulfonate tetrabutylammonium salt Adding Form of StabilizerAqueous Solution Aqueous Solution Amount of Stabilizer (ppm) 14  8 No.of Unit Process Zones  1  1 Resin Temp. (° C.) 290  290  Kneading PartPressure (mmHg)  10⁴  10⁴ Reaction Time (sec) 20 20 Vent Part Pressure(mmHg) 15 15 Reaction Time (sec) 20 20 Experimental Intrinsic Viscosity   0.347    0.345 Result b-Value of the Lab Color System   1.3   1.4Amount of Hydroxy Terminal (mol/ton) 18 15

Example 25

A polycarbonate was produced under the conditions of the Example 1except for the use of 2×10⁻⁸ equivalent of bisphenol A disodium saltbased on 1 mol of 2,2-bis(4-hydroxyphenyl)propane, and the wholequantity of the produced resin was pelletized.

The obtained pellet had an intrinsic viscosity of 0.354, a b-value ofthe Lab color system of 0.29 and a hydroxy terminal content of 95mol/ton.

The terminal blocking reaction and the addition and kneading of astabilizer were performed on the obtained polycarbonate pellet under theconditions of the Example 1 except for the use of 2 ppm of thestabilizer based on the polycarbonate.

The measured results of the amount of hydroxy terminal, the intrinsicviscosity and the b-value of the Lab color system of the finallyobtained polycarbonate resins are shown in the Table 15.

TABLE 15 Terminal Blocking Example 25 Reaction Reactor Twin ScrewExtruder Terminal Blocking Agent

Amount of the Blocking Agent (mol-equiv) 1.5 No. of Unit Process Zones 2Resin Temp. (° C.) 290 Kneading Part Pressure (mmHg) 100 Reaction Time(sec) 20 Vent Part Pressure (mmHg) 5 Reaction Time (sec) 20 ExperimentalIntrinsic Viscosity 0.348 Result b-Value of the Lab Color System 1.2Amount of Hydroxy Terminal (mol/ton) 17

What is claimed is:
 1. A process for the production of a polycarbonateby the melt polycondensation of an aromatic dihydroxy compound with anaromatic carbonic acid diester in the presence of a polycondensationcatalyst wherein after the melt polycondensation, the process comprisesadding and kneading a terminal blocking agent expressed by the followingformula (1)

into the system at 200 to 350° C. under a pressure of 1,013 hPa (760mmHg) or below for 0.1 second or longer in an amount of 0.3 to 4mol-equivalent based on the hydroxy terminal group amount of thepolycarbonate, and adding and kneading a stabilizer thereafter at 200 to350° C. under a pressure of 1.333×10⁵ hPa (10⁵ mmHg) or below for 0.1second or longer, wherein, R¹ is a chlorine atom, a methoxycarbonylgroup or an ethoxycarbonyl group; and R² is an alkyl group having 1 to30 carbons, an alkoxy group having 1 to 30 carbons, an aryl group having6 to 30 carbons or an aryloxy group having 6 to 30 carbons in which thealkyl group having 1 to 30 carbons and the alkoxy group having a 1 to 30carbons may be replaced with methoxycarbonyl, ethoxycarbonyl,(o-methoxycarbonylphenyl)oxycarbonyl or(o-ethoxycarbonylphenyl)oxycarbonyl, and the aryl group having 6 to 30carbons and the aryloxy group having 6 to 30 carbons may be substitutedwith methoxycarbonyl, ethoxycarbonyl,(o-methoxycarbonylphenyl)oxycarbonyl,(o-ethoxycarbonylphenyl)oxycarbonyl, an alkyl group having 1 to 30carbons or an alkoxy group having 1 to 30 carbons.
 2. A processdescribed in the claim 1, wherein a twin-screw extruder furnished withone or more unit process zones each comprising a kneading part and avent part is used in the addition and kneading of a terminal-blockingagent and a terminal blocking agent is added to the kneading part.
 3. Aprocess described in the claim 2, wherein the kneading part of the unitprocess zone is placed at the upstream side of the vent part and thevent part and the kneading part are directly contacted with each otherwithout a polymer seal part in between.
 4. A process described in theclaim 1, wherein at least one kind of reactor selected from a horizontalreactor and a vertical stirring tank is used in the addition andkneading of the terminal blocking agent.
 5. A process described in claim1 wherein the addition and kneading of the terminal blocking agent arecarried out at 240 to 320° C. under a pressure of 666 hPa (500 mmHg) orbelow.
 6. A process described in claim 1 wherein the system is evacuatedunder a pressure of 666 hPa (500 mmHg) or below for 0.1 second or longerafter the kneading of the terminal blocking agent.
 7. A processdescribed in claim 1 or 3, wherein the evacuation treatment after thekneading of the terminal blocking agent is carried out under a pressurelower than the pressure in the kneading of the terminal blocking agent.8. A process described in claim 1, wherein the compound expressed by theaforementioned formula (1) has a structure expressed by the followingformula (1)-1

wherein, R¹ is a chlorine atom, a methoxycarbonyl group or anethoxycarbonyl group; and R²¹ is an alkyl group having 1 to 30 carbonsor an aryl group having 6 to 30 carbons; wherein the alkyl group and thearyl group may be replaced with methoxycarbonyl, ethoxycarbonyl,(o-methoxy-carbonylphenyl)oxycarbonyl,(o-ethoxycarbonylphenyl)oxycarbonyl, an alkyl group having 1 to 30carbons or an alkoxy group having a carbon number of 1 to 30 carbons. 9.A process described in claim 1, wherein the compound expressed by theaforementioned formula (1) has a structure expressed by the followingformula (1)-2

wherein, R¹ is a chlorine atom, a methoxycarbonyl group or anethoxycarbonyl group; and R²² is an alkyl group having a 1 to 30 carbonsor an aryl group having 6 to 30 carbons, wherein the alkyl group andaryl group may be substituted with methoxycarbonyl, ethoxycarbonyl,(o-methoxy-carbonylphenyl)oxycarbonyl,(o-ethoxycarbonylphenyl)oxycarbonyl, an alkyl group having 1 to 30carbons or an alkoxy group having 1 to 30 carbons.
 10. A processdescribed in claim 1 wherein the polycondensation catalyst is composedof 1×10⁻⁷ to 1×10⁻³ equivalent as a whole, based on 1 mol of thearomatic dihydroxy compound, of an alkali metal compound and/or analkaline earth metal compound and a nitrogen-containing basic compound.11. A process described in claim 1, wherein a stabilizer is added in anamount of 0.5 to 50 mol based on 1 mol of the polycondensation catalyst.12. A process described in claim 11 wherein at least one kind ofcompound selected from sulfonic acid ammonium salts, sulfonic acidphosphonium salts and sulfonic acid esters is used as the stabilizer.13. A process described in claim 12 wherein at least one kind ofcompound selected from esters, ammonium salts and phosphonium salts ofdodecylbenzene-sulfonic acid is used as the stabilizer.
 14. A processdescribed in claim 12 wherein at least one kind of compound selectedfrom p-toluenesulfonic acid esters, p-toluenesulfonic acid ammoniumsalt, p-toluenesulfonic acid phosphonium salts, benzenesulfonic acidesters, benzenesulfonic acid ammonium salts and benzenesulfonic acidphosphonium salts is used as the stabilizer.
 15. A process described inclaim 12 wherein a twin-screw extruder having at least one unit processzone comprising a kneading part and a vent part placed at the downstreamside of the kneading part with or without a polymer seal part in betweenis used in the addition of the stabilizer, and the stabilizer is addedto the kneading part of the twin-screw extruder directly or in the stateof a solution.
 16. A process described in claim 15 wherein theevacuation treatment after the kneading of the stabilizer is carried outunder a pressure of 1,013 hPa (760 mmHg) or below for 0.1 second orlonger.
 17. A process described in claim 1 wherein the material of thereactor to perform the melt polycondensation of the polycarbonate, theaddition and kneading of the terminal blocking agent and the additionand kneading of the stabilizer is a metallic material selected fromstainless steel, nickel, nickel alloy, titanium, titanium alloy andsteel or a stainless steel or steel having nickel coating layer,titanium alloy coating layer or chromium coating layer.